Expression of glutamate uptake transporters after dibutyryl cyclic AMP differentiation and traumatic injury in cultured astrocytes

Our findings indicate that differentiation of primary astrocytes by dibutyryl cyclic adenosine monophosphate (dBcAMP) and scratch injury together resulted in increased glutamate transporter gene expression. Confluent primary cultures were prepared from cerebral cortex of normal new born rat pups. The primary cultures were then divided into four groups each: control and scratch-injured, and dBcAMP-treated control and scratch-injured cultures. Total RNA was extracted at 0, 1, 2, 4, and 7 days after injury. Expression of the electrogenic glutamate transporters, GLAST, GLT-1, and EAAC-1, was quantitated by the reverse transcriptase-polymerase chain reaction method (RT-PCR) and slot blot hybridization followed by densitometric scanning. Triplicate cultures were analyzed for each time-point. Our studies indicate that all these astrocyte cultures expressed the two glial transporters, GLAST and GLT-1, while none of the cultures expressed the neuronal transporter, EAAC-1. The expression of the two transporters in the dBcAMP-treated primary cultures were markedly increased from the non-treated cultures. The dBcAMP-treated cultures had 2- to 4-times increase in levels of GLAST and GLT-1-mRNA expression both before and after scratch injury, as compared to untreated non-injured and injured primary cultures. All of the cultures expressed GLAST in greater proportion than GLT-1. (C) 1997 Elsevier Science B.V.